Lewisite (L) is an organoarsenic compound. It was once manufactured in the U.S., Japan, Germany[2] and the Soviet Union[3] for use as a chemical weapon, acting as a vesicant (blister agent) and lung irritant. Although colorless and odorless, impure samples of lewisite are a yellow, brown, violet-black, green, or amber oily liquid with a distinctive odor that has been described as similar to geraniums.[4][5]

It can easily penetrate ordinary clothing and latex rubber gloves. Upon skin contact it causes immediate stinging, burning pain and itching that can last for 24 hours. Within minutes, a rash develops and the agent is absorbed through the skin. Large, fluid-filled blisters (similar to those caused by mustard gas exposure) develop after approximately 12 hours and cause pain for 2–3 days.[4][5] These are severe chemical burns and begin with small blisters in the red areas of the skin within 2–3 hours and grow worse, encompassing the entire red area, for the ensuing 12–18 hours after initial exposure. Liquid lewisite has faster effects than lewisite vapor.[5] Sufficient absorption can cause deadly livernecrosis.

Those exposed to lewisite can develop refractory hypotension (low blood pressure) known as Lewisite shock, as well as some features of arsenic toxicity.[7] Lewisite causes physical damage to capillaries, which then become leaky, meaning that there is not enough blood volume to maintain blood pressure, a condition called hypovolemia. When the blood pressure is low, the kidneys may not receive enough oxygen and can be damaged.[5]

Lewisite was first synthesised in 1904 by Julius Arthur Nieuwland during studies for his PhD.[9][10][11] Within his doctoral thesis he described a reaction between acetylene and arsenic trichloride, which led to the formation of lewisite.[12] Exposure to the resulting compound made Nieuwland so ill he was hospitalized for a number of days.[10]

Lewisite is named after the US chemist and soldier Winford Lee Lewis (1878–1943). In 1918 Dr John Griffin (Julius Arthur Nieuwland's thesis advisor) drew Lewis's attention to Nieuwland's thesis at Maloney Hall, a chemical laboratory at The Catholic University of America, Washington D.C..[13] Lewis then attempted to purify the compound through distillation but found that the mixture exploded on heating until it was washed with HCl.[13]

Lewisite was developed into a secret weapon (at a facility located in Cleveland, Ohio (The Cleveland Plant) at East 131st Street and Taft Avenue[14]) and given the name "G-34" (which had previously been the code for mustard gas) in order to confuse its development with mustard gas.[15] Production began at a plant in Willoughby, Ohio on November 1, 1918.[16] It was not used in World War I, but experimented with in the 1920s as the "Dew of Death".[17]

After World War I, the US became interested in lewisite because it was not flammable. It had the military symbol of "M1" up into World War II, when it was changed to "L". Field trials with lewisite during World War II demonstrated that casualty concentrations were not achievable under high humidity due to its rate of hydrolysis and its characteristic odor and lacrymation forced troops to don masks and avoid contaminated areas.[citation needed] The United States produced about 20,000 tons of lewisite, keeping it on hand primarily as an antifreeze for mustard gas or to penetrate protective clothing in special situations.

It was replaced by the mustard gas variant HT (a 60:40 mixture of sulfur mustard and O Mustard), and declared obsolete in the 1950s. It is effectively treated with British anti-lewisite (dimercaprol). Most stockpiles of lewisite were neutralised with bleach and dumped into the Gulf of Mexico,[18] but some remained at the Deseret Chemical Depot located outside of Salt Lake City, Utah,[19] although as of January 18, 2012 all U.S stockpiles were destroyed.

Producing or stockpiling lewisite was banned by the Chemical Weapons Convention. When the convention entered force in 1997, the parties declared world-wide stockpiles of 6,747 tonnes of lewisite. As of December 2015, 98% of these stockpiles had been destroyed.[20]

In 2001, lewisite was found in a World War I weapons dump in Washington, D.C.[21]

In mid-2006, China and Japan were negotiating disposal of stocks of lewisite in northeastern China, left by Japanese military during World War II. Residents of China have died over the past twenty years from accidental exposure to these stockpiles.[22]